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Type Monomer (type + monomer)
Selected AbstractsHyperbranched Polyalkoxysiloxanes via AB3 -Type MonomersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003Manfred Jaumann Abstract We have synthesized polyethoxysiloxanes starting from the AB3 -type monomers triethoxysilanol and acetoxytriethoxysilane. The polymers are liquid and soluble in organic solvents. 29Si NMR spectroscopy and MALDI-ToF mass spectrometry analyses show that the polymers have a hyperbranched structure with additional internal cyclization. 29Si NMR spectroscopy indicates that the polymer synthesized from acetoxytriethoxysilane is less branched than the polymer synthesized from triethoxysilanol. Analysis of the molar mass and mass distribution of the polymers via size exclusion chromatography (calibrated via MALDI-ToF MS and viscosimetry) yields a molar mass of Mn,,,2 kg,·,mol,1 and Mw,,,8 kg,·,mol,1 for polymers synthesized from triethoxysilanol. The molar mass of the polymers synthesized from acetoxytriethoxysilane can be controlled by variation of the polymerization time in the range of Mn,,,1.8,12 kg,·,mol,1 and Mw,,,2.1,2,200 kg,·,mol,1. Photograph of a vial containing polyethoxysiloxane obtained from triethoxysilanol and a schematic drawing of the proposed molecular structure of the polymer. [source] Kinetics of self-condensing vinyl hyperbranched polymerization in three-dimensional spaceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Xuehao He Abstract Self-condensing vinyl hyperbranched polymerization (SCVP) with A-B* type monomer is simulated applying Monte Carlo method using 3d bond fluctuation lattice model in three-dimensional space. The kinetics of SCVP with zero active energy of reaction is studied in detail. It is found that the maximal number,average and weight,average polymerization degrees and the maximal molecular weight distribution, at varying the initial monomer concentration and double bond conversion, are about 52, 190, and 3.93, respectively, which are much lower than theoretical values. The maximal average fraction of branching points is about 0.27, obtained at full conversion at the initial monomer concentration of 0.75. The simulation demonstrated the importance of steric effects and intramolecular cyclization in self-condensing vinyl hyperbranched polymerization. The results are also compared with experiments qualitatively and a good agreement is achieved. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4486,4494, 2008 [source] Hyperbranched polycarbosiloxane with dendritic boron cores: Synthesis, characterization, and structure regulationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2006Jie Kong Abstract The synthesis, characterization, and structure regulation of hyperbranched polycarbosiloxane with dendritic boron cores were realized in this paper. First, dendritic boron core was synthesized via hydroboration with borane dimethylsulfide and bis(allyloxy)dimethylsilane. Then, the hyperbranched polycarbosiloxanes with dendritic boron cores were synthesized via hydrosilylation with AB2 type monomer of bis(allyloxy)methylsilane and dendritic boron cores. The molecular structures of the dendritic boron core and resulting hyperbranched polymers were characterized by using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and 13C nuclear magnetic resonance spectroscopies. Size exclusion chromatography/multiangle laser light scattering analysis reveals that the structures of hyperbranched polycarbosiloxane can be regulated effectively by incorporation of functional dendritic boron cores. Compared with hyperbranched polycarbosiloxane of the same molecular weight level, the hyperbranched polycarbosiloxane with dendritic boron cores presents narrower molecular weight distribution as well as much smaller hydrodynamic radius and intrinsic viscosity. Thermalgravimetric analyzer analysis indicates that both the decomposition temperature and ceramic yields are increased as the results of the incorporation of dendritic boron cores into hyperbranched polycarbosiloxane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3930,3941, 2006 [source] Hydroxyl-terminated hyperbranched aromatic poly(ether-ester)s: Synthesis, characterization, end-group modification, and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Thiyagarajan Shanmugam Abstract Novel AB2 -type monomers such as 3,5-bis(4-methylolphenoxy)benzoic acid (monomer 1), methyl 3,5-bis(4-methylolphenoxy) benzoate (monomer 2), and 3,5-bis(4-methylolphenoxy)benzoyl chloride (monomer 3) were synthesized. Solution polymerization and melt self-polycondensation of these monomers yielded hydroxyl-terminated hyperbranched aromatic poly(ether-ester)s. The structure of these polymers was established using FTIR and 1H NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 2.0 × 103 to 1.49 × 104 depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End-group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4-(decyloxy)benzoic acid and methyl red dye. The end-capping groups were found to change the thermal properties of the polymers such as Tg. The optical properties of hyperbranched polymer and the dye-capped hyperbranched polymer were investigated using ultraviolet-absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414,5430, 2008 [source] Cyclic Polymers by Kinetically Controlled Step-Growth PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5-6 2003Hans R. Kricheldorf Abstract The theory of step-growth polymerizations including the cascade theory is discussed in the light of new results focussing on the role of cyclization reactions. The identification of cyclic oligomers and polymers in reaction products of step-growth polymerizations has been eased considerably by means of MALDI-TOF mass spectrometry. Experimental examples concern syntheses of polyesters, polycarbonates, polyamides, polyimides, poly(ether sulfone)s, poly(ether ketone)s and polyurethanes. It was found in all cases that the percentage and molecular weight of the cycles increases when the reaction conditions favor high molecular weights. In the absence of side reactions all reaction products will be cycles when conversion approaches 100%. Cyclization may even take place in the nematic phase but even-numbered cycles are favored over odd-numbered ones due to electronic interactions between mesogens aligned in parallel. In contrast to Flory's cascade theory, cyclization also plays a decisive role in polycondensations of abn -type monomers, and at 100% conversion all hyperbranched polymers have a cyclic core. Furthermore, it is demonstrated that in a2+b3 polycondensations intensive cyclization in the early stages of the process has the consequence that either no gelation occurs or the resulting networks consist of cyclic and bicyclic oligomers as building blocks. Finally, a comparison between cyclization of synthetic polymers and biopolymers is discussed. Schematic representation of a network structure mainly consisting of cyclic oligomers and multicyclic building blocks as derived from "a2" + "b3" polycondensation. [source] | ||||||||||